Through thermal test, cold state experiment, analysis and simulation of thermal process, the gas flow distribution in pelletizing shaft furnace （PSF） was discussed. The results show that there are five flowing trend...Through thermal test, cold state experiment, analysis and simulation of thermal process, the gas flow distribution in pelletizing shaft furnace （PSF） was discussed. The results show that there are five flowing trends among them, the downward roasting gas and the upward cooling gas are the most unsteady, which influence flow distribution greatly. Among the operating parameters, the ratio of inflow is a key factor affecting the flow distribution. The roasting and cooling gases will entirely flow into the roasting zone and internal vertical air channels （IVAC）, respectively, if the ratio of inflow is critical. From such a critical operating condition increasing roasting gas flow or decreasing cooling gas flow, the roasting gas starts flowing downwards so as to enter the inside of IVAC the greater the ratio of inflow, the larger the downward flowrate. Among constructional parameters, the width of roasting zone b1, width of IVAC b2 and width of cooling zone b3, and the height of roasting zone h1, height of soaking zone h2 and height of cooling zone hs are the main factors affecting flow distribution. In case the ratio of b2/b3, or h3/h2, or h1/h2 is increased, the upward cooling gas tends to decrease while the downward roasting gas tends to increase with a gradual decrease in the ratio of inflow.展开更多
Based on the laboratory experiment of reducing iron ore-coal pellet in oxidizing atmosphere,a new self-heating reduction method of iron ore-coal pellet in the cocurrent shaft furnace(CSF) has been developed.In this pr...Based on the laboratory experiment of reducing iron ore-coal pellet in oxidizing atmosphere,a new self-heating reduction method of iron ore-coal pellet in the cocurrent shaft furnace(CSF) has been developed.In this process,the pellets and preheated oxygen-enriched air enter the shaft furnace through its top and descend cocurrently in the furnace.Most of the heat required for rising temperature and endothermic reduction of descending pellets is provided by the way that the descending air burns the volatile from pellets and CO from the reduction of iron oxide in pellets.The reduced pellets and high temperature gas are discharged from the lower part.The sensible heat and chemical energy of the off-gas are used to heat the oxygen-enriched air in stove.This process is applicable to the direct reduction of iron pellets and prereduction of iron pellets in smelting reduction with iron bath.展开更多
The downward moving behavior of pellets in a 8 m2 pellet shaft furnace with an internal vertical air channel and a drying bed was studied by means of a visualized model(1-15) and a top model(1-1).The visualized model ...The downward moving behavior of pellets in a 8 m2 pellet shaft furnace with an internal vertical air channel and a drying bed was studied by means of a visualized model(1-15) and a top model(1-1).The visualized model experiment shows that the downward movement of pellets can be regarded as plug flow approximately inside the furnace except for the lower region of cooling zone due to the influence of the drained hopper.The top model experiment reveals that the pellet sizes increase along the moving direction because of the percolation phenomenon,which results in a decrease of the resistance coefficient and an increase of the gas flow rate from the furnace wall toward the furnace center.展开更多
When carbon-bearing pellets of oolitic hematite are treated in a shaft furnace,some problems are typically encountered：the metallization ratio of the metal pellets is low;the carbon-bearing pellets bond with each oth...When carbon-bearing pellets of oolitic hematite are treated in a shaft furnace,some problems are typically encountered：the metallization ratio of the metal pellets is low;the carbon-bearing pellets bond with each other at high temperatures;and the separation of phosphorus from iron is difficult.To solve these problems,experiments were conducted on oolitic hematite reduction in a resistance furnace and semi-industrial test shaft furnace.The results showed that the metallization rate reached 90% or greater under the conditions of a reduction temperature of 1 150℃,an atmosphere of simulated flue gas,and a reduction time between 1.5and 2.0h.The problem of high-temperature bonding among pellets can be solved by increasing the strength of the pellets,coating their surface with a surface transfer agent and maintaining an even temperature inside the shaft furnace.The basicity of the ore blend exerted no obvious effect on the magnetic concentrate and phosphorus content.The phosphorus content in the magnetic concentrate can be further reduced by improving the grinding capacity of the ball mills used in the experiments.On the basis of the experimental results related to oolitic hematite reduction with carbon-bearing pellets in a shaft furnace,the experimental requirements were satisfied with an average 88.27%total Fe content and 0.581% P content in the pellets.展开更多
The technology of coal gasification in shaft furnace is an effective way to develop direct reduction iron in China. In order to clarify the process of the reduction of oxidized pellets in shaft furnace by carbon monox...The technology of coal gasification in shaft furnace is an effective way to develop direct reduction iron in China. In order to clarify the process of the reduction of oxidized pellets in shaft furnace by carbon monoxide or hydrogen in two ways, i.e. thermodynamics and kinetics, the gas utilization and reaction mechanism were studied by theoretical computations and isothermal thermogravimetric experiment. The results showed that the gas utilization increased with the rise of temperature when xH2/xco≥1 and with the increase of xco/（xH2 ＋xco） when temperature is less than 1073 K. The water-gas shift reaction restrains efficient utilization of gas, particularly in high tem- perature and hydrogen-rich gas. The gas utilization dropped with increase of carburization quantity of direct reduction iron （DRI） and oxygen potential of atmosphere. With the increase of both temperature and content of H2 in inlet gas, the reaction rate increased. At 100% Hz atmosphere, the interfacial chemical reaction is the dominant reaction re- stricted step. For the H2-CO mixture atmosphere, the reduction process is controlled by both interfacial chemical reaction and internal diffusion展开更多
Efficient utilization of sinter return fine is an important measure to reduce cost,increase efficiency,save energy and reduce emission.A new path of green and efficient utilization of return fine was proposed to produ...Efficient utilization of sinter return fine is an important measure to reduce cost,increase efficiency,save energy and reduce emission.A new path of green and efficient utilization of return fine was proposed to produce composite pellets.The metallurgical properties of composite pellets under the condition of hydrogen-rich blast furnace were studied.The experimental results indicate that the coated concentrate was consolidated for the composite pellets through normal Fe_(2)O_(3) recrystallization.Near the surface of core return fine,the liquid phase formed due to its low-melting point,assimilated the adjacent concentrate,and then consolidated with the temperature decreasing.Compared with regular pellets,the com-pressive strength and reduction swelling index of composite pellets were decreased,but the reducibility index and softening-melting properties were improved.In addition,the reduction degradation index of composite pellets was sig-nificantly higher than that of sinter.Therefore,adding composite pellets was conducive to indirect reduction in blast furnace,reducing fuel ratio and improving production efficiency.According to the effect of the roasting system on the metallurgical properties,the roasting temperature and time were determined as 1250℃and 30 min,respectively.The composite pellets can be produced under the traditional pelletizing process.展开更多
After taking into account the conditions of the domestic iron resources and the non-coking coal resources, the process of coal gasification-shaft furnace is an effective way to develop direct reduction iron in China. ...After taking into account the conditions of the domestic iron resources and the non-coking coal resources, the process of coal gasification-shaft furnace is an effective way to develop direct reduction iron in China. The following tasks are very critical to choose suitable process of shaft furnace and gasification, including the production of oxidized pellets with excellent comprehensive properties as well as the study of the reaction behavior and mechanism of swelling. The results showed that the oxidized pellets of using domestic magnetic iron concentrate as raw materials have favorable comprehensive properties, including higher mechanical strength both before and after reduction, faster reduction rate and lower reduction swelling index (RSI). All of these properties can meet the shaft furnace yielding requirement. When the temperature was below 1 223 K, the pellets′ RSI was lower than 20%. With increasing of the content of H2 in atmosphere, the pellets reaction rate accelerated, crushing strength enhanced and RSI decreased. The RSI dropped to 10.26% at 1 323 K in 100% H2 atmosphere, and it is up to 39.88% in 100% CO atmosphere. The iron grains mainly presented in platelike when pellets were reduced by H2, however, in CO atmosphere the iron grains were precipitated in flocculent. The whisker shape of iron grains and heating effects of reduction reaction are the major factors leading to the poor pellets strength and increase of RSI. Appropriately controlling the temperature and increasing the ratio of H2 to CO in atmosphere are good for dropping the RSI.展开更多
An experiment for the oxidation process of single magnetite pellet and theoretical analysis based on modi lied unreacted core shrinking （MUCS） model were carried out, and the controlling mechanisms of the initial an...An experiment for the oxidation process of single magnetite pellet and theoretical analysis based on modi lied unreacted core shrinking （MUCS） model were carried out, and the controlling mechanisms of the initial and de veloping reactions were examined, respectively. From the study of the initial reaction, it was found that the chemical reaction of surface is the controlling step of the overall reaction when the temperature is up to about 750 K, while the mass transfer through the gaseous boundary layer dominates the reaction rate when the temperature is above 750 K. As the reaction developing within the pellet, the mass transfer through the produced layer becomes the controlling step. In addition, the effects of reaction conditions （such as oxygen concentration, temperature） on the fractional oxidation of magnetite pellet were determined.展开更多
The influence of basicity on the metallurgical performances and reduction characteristics of fired super high-grade magnetite pellets under the simulated shaft furnace gas conditions was investigated.The fired pellets...The influence of basicity on the metallurgical performances and reduction characteristics of fired super high-grade magnetite pellets under the simulated shaft furnace gas conditions was investigated.The fired pellets in the basicity range of 0.09(natural basicity)to 1.00 show superior reducibility and low-temperature disintegration performance.However,in the basicity range of 0.20–0.80,the abnormal swelling of the fired pellets occurs.Improving basicity from 0.09 to 0.40 promotes the generation of low melting point slag phases and lower porosity of fired pellets,and accelerates the growth and densification of hematite crystals,impeding the reduction of hematite particles and the formation of metallic iron shell.In addition,the slags that distribute between the hematite particles absorb the reduction stresses by increased distances between the particles during the reduction process,which leads to the large reduction swelling of pellets.展开更多
基金ItemSponsored by National Natural Science Foundation of China (50334020) National Key Fundamental Research andDevelopment Project of China (2000026300)
文摘Through thermal test, cold state experiment, analysis and simulation of thermal process, the gas flow distribution in pelletizing shaft furnace （PSF） was discussed. The results show that there are five flowing trends among them, the downward roasting gas and the upward cooling gas are the most unsteady, which influence flow distribution greatly. Among the operating parameters, the ratio of inflow is a key factor affecting the flow distribution. The roasting and cooling gases will entirely flow into the roasting zone and internal vertical air channels （IVAC）, respectively, if the ratio of inflow is critical. From such a critical operating condition increasing roasting gas flow or decreasing cooling gas flow, the roasting gas starts flowing downwards so as to enter the inside of IVAC the greater the ratio of inflow, the larger the downward flowrate. Among constructional parameters, the width of roasting zone b1, width of IVAC b2 and width of cooling zone b3, and the height of roasting zone h1, height of soaking zone h2 and height of cooling zone hs are the main factors affecting flow distribution. In case the ratio of b2/b3, or h3/h2, or h1/h2 is increased, the upward cooling gas tends to decrease while the downward roasting gas tends to increase with a gradual decrease in the ratio of inflow.
基金Project supported by the National Foundation of Nature Science of China
文摘Based on the laboratory experiment of reducing iron ore-coal pellet in oxidizing atmosphere,a new self-heating reduction method of iron ore-coal pellet in the cocurrent shaft furnace(CSF) has been developed.In this process,the pellets and preheated oxygen-enriched air enter the shaft furnace through its top and descend cocurrently in the furnace.Most of the heat required for rising temperature and endothermic reduction of descending pellets is provided by the way that the descending air burns the volatile from pellets and CO from the reduction of iron oxide in pellets.The reduced pellets and high temperature gas are discharged from the lower part.The sensible heat and chemical energy of the off-gas are used to heat the oxygen-enriched air in stove.This process is applicable to the direct reduction of iron pellets and prereduction of iron pellets in smelting reduction with iron bath.
基金Projects(59374166,58974155) supported by the National Natural Science Foundation of China
文摘The downward moving behavior of pellets in a 8 m2 pellet shaft furnace with an internal vertical air channel and a drying bed was studied by means of a visualized model(1-15) and a top model(1-1).The visualized model experiment shows that the downward movement of pellets can be regarded as plug flow approximately inside the furnace except for the lower region of cooling zone due to the influence of the drained hopper.The top model experiment reveals that the pellet sizes increase along the moving direction because of the percolation phenomenon,which results in a decrease of the resistance coefficient and an increase of the gas flow rate from the furnace wall toward the furnace center.
基金Item Sponsored by National Science and Technology Support Program for 12th Five-year Plan of China(2013BAE07B03)
文摘When carbon-bearing pellets of oolitic hematite are treated in a shaft furnace,some problems are typically encountered：the metallization ratio of the metal pellets is low;the carbon-bearing pellets bond with each other at high temperatures;and the separation of phosphorus from iron is difficult.To solve these problems,experiments were conducted on oolitic hematite reduction in a resistance furnace and semi-industrial test shaft furnace.The results showed that the metallization rate reached 90% or greater under the conditions of a reduction temperature of 1 150℃,an atmosphere of simulated flue gas,and a reduction time between 1.5and 2.0h.The problem of high-temperature bonding among pellets can be solved by increasing the strength of the pellets,coating their surface with a surface transfer agent and maintaining an even temperature inside the shaft furnace.The basicity of the ore blend exerted no obvious effect on the magnetic concentrate and phosphorus content.The phosphorus content in the magnetic concentrate can be further reduced by improving the grinding capacity of the ball mills used in the experiments.On the basis of the experimental results related to oolitic hematite reduction with carbon-bearing pellets in a shaft furnace,the experimental requirements were satisfied with an average 88.27%total Fe content and 0.581% P content in the pellets.
基金Item Sponsored by National Natural Science Foundation of China(51090384)Fundamental Research Funds for Central Universities of China(N110202001)
文摘The technology of coal gasification in shaft furnace is an effective way to develop direct reduction iron in China. In order to clarify the process of the reduction of oxidized pellets in shaft furnace by carbon monoxide or hydrogen in two ways, i.e. thermodynamics and kinetics, the gas utilization and reaction mechanism were studied by theoretical computations and isothermal thermogravimetric experiment. The results showed that the gas utilization increased with the rise of temperature when xH2/xco≥1 and with the increase of xco/（xH2 ＋xco） when temperature is less than 1073 K. The water-gas shift reaction restrains efficient utilization of gas, particularly in high tem- perature and hydrogen-rich gas. The gas utilization dropped with increase of carburization quantity of direct reduction iron （DRI） and oxygen potential of atmosphere. With the increase of both temperature and content of H2 in inlet gas, the reaction rate increased. At 100% Hz atmosphere, the interfacial chemical reaction is the dominant reaction re- stricted step. For the H2-CO mixture atmosphere, the reduction process is controlled by both interfacial chemical reaction and internal diffusion
基金financial support from the National Natural Science Foundation of China (U1960205)China Minmetals Science and Technology Special Plan Foundation (2020ZXA01).
文摘Efficient utilization of sinter return fine is an important measure to reduce cost,increase efficiency,save energy and reduce emission.A new path of green and efficient utilization of return fine was proposed to produce composite pellets.The metallurgical properties of composite pellets under the condition of hydrogen-rich blast furnace were studied.The experimental results indicate that the coated concentrate was consolidated for the composite pellets through normal Fe_(2)O_(3) recrystallization.Near the surface of core return fine,the liquid phase formed due to its low-melting point,assimilated the adjacent concentrate,and then consolidated with the temperature decreasing.Compared with regular pellets,the com-pressive strength and reduction swelling index of composite pellets were decreased,but the reducibility index and softening-melting properties were improved.In addition,the reduction degradation index of composite pellets was sig-nificantly higher than that of sinter.Therefore,adding composite pellets was conducive to indirect reduction in blast furnace,reducing fuel ratio and improving production efficiency.According to the effect of the roasting system on the metallurgical properties,the roasting temperature and time were determined as 1250℃and 30 min,respectively.The composite pellets can be produced under the traditional pelletizing process.
基金Item Sponsored by National Natural Science Foundation of China (51090384)Fundamental Research Funds for Central Universities of China (N090602005,N110202001)
文摘After taking into account the conditions of the domestic iron resources and the non-coking coal resources, the process of coal gasification-shaft furnace is an effective way to develop direct reduction iron in China. The following tasks are very critical to choose suitable process of shaft furnace and gasification, including the production of oxidized pellets with excellent comprehensive properties as well as the study of the reaction behavior and mechanism of swelling. The results showed that the oxidized pellets of using domestic magnetic iron concentrate as raw materials have favorable comprehensive properties, including higher mechanical strength both before and after reduction, faster reduction rate and lower reduction swelling index (RSI). All of these properties can meet the shaft furnace yielding requirement. When the temperature was below 1 223 K, the pellets′ RSI was lower than 20%. With increasing of the content of H2 in atmosphere, the pellets reaction rate accelerated, crushing strength enhanced and RSI decreased. The RSI dropped to 10.26% at 1 323 K in 100% H2 atmosphere, and it is up to 39.88% in 100% CO atmosphere. The iron grains mainly presented in platelike when pellets were reduced by H2, however, in CO atmosphere the iron grains were precipitated in flocculent. The whisker shape of iron grains and heating effects of reduction reaction are the major factors leading to the poor pellets strength and increase of RSI. Appropriately controlling the temperature and increasing the ratio of H2 to CO in atmosphere are good for dropping the RSI.
基金Sponsored by National Natural Science Foundation of China(59374166,11072057)
文摘An experiment for the oxidation process of single magnetite pellet and theoretical analysis based on modi lied unreacted core shrinking （MUCS） model were carried out, and the controlling mechanisms of the initial and de veloping reactions were examined, respectively. From the study of the initial reaction, it was found that the chemical reaction of surface is the controlling step of the overall reaction when the temperature is up to about 750 K, while the mass transfer through the gaseous boundary layer dominates the reaction rate when the temperature is above 750 K. As the reaction developing within the pellet, the mass transfer through the produced layer becomes the controlling step. In addition, the effects of reaction conditions （such as oxygen concentration, temperature） on the fractional oxidation of magnetite pellet were determined.
基金The authors want to express their gratitude for the financial support from the National Natural Science Foundation of China(No.52004075)Science and Technology Planning Projects of Guizhou Province(No.ZK[2021]262)+1 种基金Program Foundation for Talents of Guizhou University(No.(2020)15)the Hunan Provincial Co-innovation Center for Clean and Efficient Utilization of Strategic Metal Mineral Resources.
文摘The influence of basicity on the metallurgical performances and reduction characteristics of fired super high-grade magnetite pellets under the simulated shaft furnace gas conditions was investigated.The fired pellets in the basicity range of 0.09(natural basicity)to 1.00 show superior reducibility and low-temperature disintegration performance.However,in the basicity range of 0.20–0.80,the abnormal swelling of the fired pellets occurs.Improving basicity from 0.09 to 0.40 promotes the generation of low melting point slag phases and lower porosity of fired pellets,and accelerates the growth and densification of hematite crystals,impeding the reduction of hematite particles and the formation of metallic iron shell.In addition,the slags that distribute between the hematite particles absorb the reduction stresses by increased distances between the particles during the reduction process,which leads to the large reduction swelling of pellets.
